1. Field of the Invention
The present invention relates to an inspection apparatus and an inspection method for inspecting a pattern formed on a surface of a semiconductor wafer, a liquid crystal substrate, or the like.
2. Related Background Art
Various methods have been proposed, in order to determine quality of a pattern formed on the surface of a semiconductor wafer, which measure a sectional form of the pattern upon observation by a scanning type electronic microscope (SEM). Measurement of a sectional form of a pattern by SEM is performed by scanning with electron beams applied on the pattern on a subject substrate in the sectional direction of the pattern, and detecting and analyzing reflection electrons or secondary electrons from the pattern so as to obtain the sectional form of the scanned part. This operation is performed on several points on the pattern, so as to determine the correctness of a form of the whole pattern. It is further checked whether there is any problem in an exposure process or an etching process for forming a pattern from the sectional form of the pattern, or whether appropriate process conditions are selected. For example, as to the exposure process, correlation between an exposure condition and the sectional form of a pattern is obtained in advance, so as to determine whether or not the exposure condition of an exposure apparatus should be corrected from the sectional form of the inspected pattern, and to obtain an appropriate exposure condition on the basis of the correlation described above, if the correction is needed. As to the etching process, correlation between conditions such as a type of a gas, a pressure of the gas and accelerating voltage and the sectional form of the pattern is obtained in advance, and the same condition check is performed. It has been disclosed in Japanese Patent Application Laid-Open No. 2003-302214.
As described above, since irradiation with electron beams on the pattern to scan is performed several times repeatedly in the measurement by SEM, an enormous time is required for obtaining the form of a pattern. Also, since the observation magnification is high, it is difficult to obtain all of the pattern forms on a wafer, which results in that several patterns are sampled to be inspected for determining the quality of the whole wafer. As a result, any defect in a part other than the sampled ones may be overlooked. Also, in a resist pattern, when electron beams are applied, the electron beams are absorbed and charged by the resist owing to accelerating voltage, so that the number of the patterns is reduced. In some cases, discharge of electricity occurs and a pattern may fall down, which may bring about inconveniences in subsequent processes. As a result, the optical observation conditions are also calculated by varying the accelerating voltage, the observation magnification, and so on. For this reason, still more time is required for the measurement.
According to the prior art, there occurs a problem that a trouble of an exposure apparatus or an etcher can not be fully detected by such overlooking. Also, since an enormous time is required for the measurement, any trouble of the exposure apparatus or the etcher which is detected from the measurement can not be fed back to these apparatuses swiftly.